1. Field of the Invention
Hybrid DNA technology provides new opportunities for preparing a wide variety of novel compounds having enhanced or unique properties. Cellular life is dependent upon the ability to perform enzyme reactions which provide energy for the cell and produce components essential to the cell's viability. Where a number of cells coexist in relative proximity, it has been frequently of interest to be able to select for one group of cells as against the other group of cells. This mode of selection has found extensive use in hybrid DNA technology in selecting for transformants and transductants.
For the most part, antibiotic resistance has been employed as a marker which is introduced into the cell in conjunction with one or more other structural genes of interest. There are numerous other situations, where one is interested in selecting for cells, where a group of cells is undesired. Coming within such categories are such diverse situations as oncogenesis, where one wishes to selectively destroy tumor cells, in the use of herbicides, where one wishes to select for a crop plant as against a weed, and in therapy against pathogens, where one wishes to destroy an invading microorganism while having minimal effect on the host. The opportunity to introduce DNA in a form where it can express enhanced resistance to a biocidal agent permits one to use enhanced amounts of the biocidal reagents while protecting the host against any detrimental effect from the biocide or biostat.
In those situations, where protection is afforded by producing an enzyme which is insensitive to the biocide or can destroy the biocide, the mutated gene affords a new product which can have a wide variety of useful properties. Enzymes can be used as labels, particularly in diagnostic assays, for the production of products, in assaying for substrates and inhibitors, purification, and the like. The ability to modify an enzyme's specificity can allow for the catalysis of reactions otherwise not available to the enzyme, enhanced activity of the enzyme, or enhanced selectivity of the enzyme.
2. Brief Description of the Prior Art
Hollander and Amrheim, Plant Physiol. (1980) 66:823-829; Amrheim et al., ibid. (1980) 66:830-834 and Steinruecken and Amrheim, Biochem. Biophys. Res. Comm. (1980) 94:1207-1212, report the biochemical characterization of a target site for glyphosate. This site was identified as a step of the shikimic acid pathway present in plants and bacteria in providing the precursor to aromatic amino acids.